What is an ACL? The ACL is the Anterior Cruciate Ligament, or one of two crossing ligaments in the middle of the knee. Basically, the ligaments are soft tissue bands that stabilize the knee. The function of the ACL is to prevent the tibia from moving too far forward on the femur.
What is an ACL tear? ACL tears are one of the more common knee injuries that people are aware of given that (relatively) high numbers of these injuries happen in professional and recreational sports. Most likely, you or someone you know has had an ACL injury. ACL tears commonly happen with cutting, pivoting, and jumping sports such as soccer, basketball, football, lacrosse, and volleyball. Patients usually feel or hear a pop at the time of injury; their knee will feel unstable or ‘give out’ from under them. These injuries usually occur without contact with another player or can happen when the player is all alone. The knee swells up significantly and there can be bruising associated with the injury. When something this significant happens, evaluation by an orthopedist is required prior to returning to sports. ACL tears are most often treated with reconstruction or replacement of the ligament with a new ligament.
How, if at all, is the female ACL different from a male ACL? Structurally, there is no difference between a female ACL and a male ACL. Both are made of collagen fibers (little ropes) that stretch from the femur to the tibia in the center of the knee. There are some differences in the laxity (stretchiness) of the ligaments based on the different hormonal variations in people as well as each person’s individual flexibility. Studies have shown that females have an increase in knee laxity and overall ligament laxity compared to male peers. Additionally, the menstrual cycle and the changing hormone concentrations may play a role in ligament laxity and risk of ACL injury.
Are females more at risk for tears? Females are at higher risk for ACL tears based on several factors. First, there are the hormonal variations and the increased overall ligament laxity in females compared to males. Additionally, females have different muscle group activation and strength during jumping and landing evaluations compared to males. The lack of muscle group activation at the time of landing has been shown to increase ACL tear risk. Females have wider hips than males and thus a wider Q angle which is a measure leg alignment and an increased Q angle is a risk factor for ACL tears.
How can female athletes protect themselves against ACL tears? Female athletes can do a lot of preventative exercises to decrease the risk of an ACL tear. While several of the risk factors that females have can’t be changed, muscle strength and muscle activation during certain activities (such as running, cutting, jumping, and landing) can be modified through ACL prevention exercises to decrease the risk of an ACL tear. Studies have shown that ACL prevention programs for teams have decreased the risk of ACL tears in those teams.
Is there any nuance to ACL reconstruction for a female patient? The ACL reconstruction surgery for males and females is very similar. There are several pre-operative discussions that play an important role in the decision to proceed with surgery. One of the more important decisions is what tissue (or graft) to use to replace the torn ACL. The options are patella tendon autograft (‘auto’ means the tendon is from the patient), hamstring autograft, or soft tissue allograft (‘allo’ means the tissue is from a cadaver). In young female athletes, the amount of flexibility in the knee is an important factor in determining which graft to choose. For patients with loose joints and very flexible ligaments who desire to return to competitive sports such as soccer, I generally favor patella tendon autografts. For patients who do not have loose joints and who want to continue to be active, I generally favor hamstring autografts. The graft decision is an important one and is determined with the patient and the treating physician.
What does recovery look like for a female ACL patient? ACL recovery is somewhat long, mostly due to letting the new ACL heal into position, remodel, and become a new ligament. This can take more than 6 months. Another important aspect of recovery is getting the muscle strength and control to return. It is amazing how quickly the muscles start to weaken after an ACL injury and surgery. Muscle control and strength can take 9-12 months to return to normal. For this reason, ACL recovery is generally between 9-12 months depending on each patient’s overall rehabilitation. One of the most important parts about rehabilitation from an ACL injury is to not allow the patient to return to play before minimizing the risk of another ACL tear as much as possible. The risk will never be 0%, but the idea of ACL prevention and ACL rehabilitation is to decrease the chance of having another ACL tear.
Dr. Moira McCarthy is an orthopedic surgeon specializing in sports medicine. She practices at both the HSS Outpatient Center in Stamford, CT and the hospital’s main campus in New York.